Thegerenuk[a] (Litocranius walleri), also known as thegiraffe gazelle, is a long-necked, medium-sizedantelope found in parts ofEast Africa. Thesole member of thegenusLitocranius, the gerenuk was firstdescribed by the naturalistVictor Brooke in 1879. It is characterised by its long, slender neck and limbs. The antelope is 80–105 centimetres (2 feet 7 inches – 3 feet 5 inches) tall, and weighs between 18 and 52 kilograms (40 and 115 pounds). Two types of colouration are clearly visible on the smoothcoat: the reddish brown back or the "saddle", and the lighter flanks, fawn to buff. Thehorns, present only on males, are lyre-shaped. Curving backward then slightly forward, these measure 25–44 cm (10–17+1⁄2 in).
The gerenuk was firstdescribed byVictor Brooke in 1879 on the basis of three malespecimens procured on "the mainland of Africa, north of the island of Zanzibar".[3] Brooke used thescientific nameGazella walleri, on the request of Gerald Waller (who provided the specimens) to name it after his deceased brother.[3] Thetype locality was later corrected byJohn Kirk, who originally obtained the specimens on the "coast near theRiver Juba in southernSomalia" before giving them to Waller.[4] In 1886,Franz Friedrich Kohl proposed a new genus for the gerenuk,Litocranius.[5] The common name derives from theSomali name for the animal (gáránúug); the first recorded use of the name dates back to 1895.[6] It is also known as the "giraffe gazelle" due to its similarity to thegiraffe.[7]
Twosubspecies have been proposed, but these are considered to be independent species by some authors.[2][8][9][10]
L. w. sclateri (Northern gerenuk or Sclater's gazelle)Neumann, 1899: Its range extends from northwestern Somalia (Berbera District) westward to touch the Ethiopian border and Djibouti.
L. w. walleri (Southern gerenuk or Waller's gazelle)(Brooke, 1879): Its range extends through northeastern Tanzania through Kenya toGalcaio (Somalia). The range lies north of theShebelle River and near Juba River.
Close-up view of a male. Note the white facial markings and the lyre-shaped horns.
The gerenuk is a notably tall, slenderantelope that resemblesgazelles. It is characterised by its long, slender neck and limbs, the flat, wedge-like head and the large, round eyes. Males are nearly89–105 cm (35–41+1⁄2 in) tall, and the shorter females 80–100 cm (31–39 in); the head-and-body length is typically between 140 and 160 cm (55 and 63 in). Males weigh between 31 and 52 kg (68 and 115 lb); females are lighter, weighing 28–45 kg (62–99 lb). The species issexually dimorphic. The tail, that ends in a black tuft, measures 25–35 cm (10–14 in).[9][13]
Two types of colouration are clearly visible on the smoothcoat: the reddish browndorsal parts (the back or the "saddle"), and the lighter flanks, fawn to buff. The underbelly and insides of the legs are cream in colour. The eyes and the mouth are surrounded by white fur. Females have a dark patch on thecrown. Thehorns, present only on males, are lyre-like (S-shaped). Curving backward then slightly forward, these measure25–44 cm (10–17+1⁄2 in).[13][9]
The gerenuk resembles thedibatag, with which it issympatric in eastern and central Somalia and southeastern Ethiopia. Both arebrachyodonts and share several facial andcranial features, along with a two-tone colouration of the coat and strong thick horns (only in males).[14] However, there are also some features distinguishing it from the gerenuk, including major morphological differences in horns, horn cores, tail,postorbital area andbasioccipital processes. The gerenuk has a longer, heavier neck and a shorter tail.[9] A finer point of difference is the absence of an inward-curving lobe in the lower edge of the ear (near its tip) in the gerenuk.[14] The subspecies of the gerenuk are similar in colouration; the southern gerenuk is the smaller of the two.[9] The Gerenuk stages of growth have a timespan from 4 months to 2.5 years: at four months, their shoulder height is about two-thirds of adult female, at six months their shoulder height is about three-quarters of adult female, at eight months their horn tips are clearly visible (about 1cm long), at one year their shoulder height is nearly equal to adult female but body more lightly built, their horns are slightly less than half ear-length, then curve, at two years their horns are about 1.5 times their ear length and the second curve becomes noticeable with the tips turning forwards, and finally at two and a half years the double curve in the horns are nearly completed.[15]
The gerenuk is adiurnal animal (active mainly during the day), though it typically stands or rests in shade during the noon. Foraging and feeding is the major activity throughout the day; females appear to spend longer time in feeding. The gerenuk may expose itself to rain, probably to cool its body.[16] The social structure consists of small herds of two to six members. Herds typically comprise members of a single sex, though female herds additionally have juveniles. Some males lead a solitary life.[9]
Fighting and travel are uncommon, possibly as a strategy to save energy for foraging.[7] Both sexes maintainhome ranges3–6 km2 (1–2+1⁄2 sq mi) large, and might overlap. Those of males are scent-marked withpreorbital gland secretions and guarded - hence these may be termedterritories. The sedentary tendency of the antelope appears to increase with age.[10]
Primarily abrowser, the gerenuk feed on foliage of bushes as well as trees, shoots, herbs, flowers and fruits.[17] It can reach higher branches and twigs better than other gazelles and antelopes by standing erect on its hindlegs and elongating its neck; this helps it reach over 2 m (6 ft 7 in) above the ground.[10]Acacia species are eaten whenever available,[10] while evergreen vegetation forms the diet during droughts.[13] The pointed mouth assists in extracting leaves from thorny vegetation.[10] The gerenuk does not drink water regularly.[17] Major predators of the antelope includeAfrican wild dogs,cheetahs,hyenas,lions andleopards.[9]
Gerenuk reproduce throughout the year. Females reachsexual maturity at around one year, and males reach sexual maturity at 1.5 years, although in the wild they may only be successful after acquiring a territory (perhaps 3.5 years).[17] Thegestation period is about seven months. They are born one at a time, weighing about 3 kg (7 lb) at birth. Offspring were produced throughartificial insemination for the first time in 2010 atWhite Oak Conservation inYulee, Florida. Four female calves were born, and one of the four was later inseminated successfully by White Oak and SEZARC (South-East Zoo Alliance for Reproduction & Conservation), creating a second generation of calves born from artificial insemination.[18] Gerenuk can live thirteen years or more in captivity, and at least eight years in the wild.[17]
^abcdefgCastelló, J. R. (2016)."Gerenuk".Bovids of the World: Antelopes, Gazelles, Cattle, Goats, Sheep, and Relatives. Princeton: Princeton University Press. pp. 158–63.ISBN978-0-691-16717-6.
^abcdeKingdon, J. (2015)."Gerenuk".The Kingdon Field Guide to African Mammals (2nd ed.). London: Bloomsbury. pp. 569–571.ISBN978-1-4729-1236-7.
^abMacdonald, D. W. (20 November 2014)."GerenukLitocranius walleri". In Kingdon, J.; Happold, D.; Hoffmann, M.; Butynski, T.; Happold, M.; Kalina, J. (eds.).Mammals of Africa. Vol. VI–Hippopotamuses, Pigs, Deer, Giraffe and Bovids. Bloomsbury. pp. 387–90.ISBN978-1-4081-8994-8.
^Leuthold, W. (1978). On the Ecology of the Gerenuk Litocranius walleri. Journal of Animal Ecology, 47(2), 561–580.https://doi.org/10.2307/3801
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